The objectives of the study are: To assess the effects on tests of intelligence and behavior of phenobarbital, a commonly prescribed anticonvulsant in children. The design of this study permits comparison of measures of tested intelligence and of behavior in children with febrile seizures who have been treated with phenobarbital, and in a group of seizure free control children. A comparison of the groups allows assessment of benefit and risk of treatment for a common childhood neurologic problem. The continued analysis efforts for the Phenobarbital Clinical Trial will be subsumed under the Intramural Research Project "Epilepsy Neuroepidemiology" (ZO1 NS 02715-04). The data collection phase is considered completed.